Portable ground thawing system and method

ABSTRACT

A portable ground thawing system for excavating Shovel Test Pits (STPs) includes a cylindrical heat chamber having an open bottom and a closed top. A charging inlet is disposed on one side and a flue is on the other. An adjustable baffle is stationed in the flue. A salamander style heater is positioned to emit a stream of hot gas through the charging inlet, creating a swirling internal current of hot gas that loops through an internal heat loft. The heat loft provides both radiant heat properties as well as supports convection via the gas current that sweep across the frozen ground before exiting the flue. Electricity to power the heater is supplied by a generator. The method of use includes orienting the heat chamber so that its charging inlet is leeward and its flue is windward relative to the prevailing wind direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Provisional Patent Application US62/929,190 filed on Nov. 1, 2019, the entire disclosure of which ishereby incorporated by reference and relied upon.

BACKGROUND OF THE INVENTION Field of the Invention.

The invention relates generally to a portable ground thawing system andmethod for placing shovel test pits (STPs) in frozen ground.

Description of Related Art.

Prior to developing a tract of land, it is sometimes required to make anarchaeological survey to determine whether the planned development mightnegatively impact ancient cultural remains, buried artifacts or othergenerally hidden objects of historical value.

A shovel test pit (STP) is a standard method for performing an initialassessment phase of an archaeological survey. In many cases, shoveltesting strategies are designed to identify archaeological resources andto delineate their boundaries. Within a specified project area, a seriesof small test holes are dug by hand using a shovel (typically) in orderto determine whether the soil contains cultural remains. A hand shovelis used due to its relative gentleness and finesse compared to chippingor hacking with an axe pick, or other forms of aggressive digging.Artifacts buried in the soil are less likely to be damaged using a handshoveling technique, through which haptic feedback can inform a trainedtechnician of conditions as they are encountered. Soil excavated fromthe STP is sifted or screened through a wire mesh to determine whetherany relevant artifacts are contained in the soil. The collected resultsof STP findings can be mapped over the project area to determine whetherfurther archaeological investigation is necessary.

The depth of an STP depends on the depth at which either the bedrock orthe sterile subsoil is found. Occasionally the excavation of shovel testpits (STPs) into frozen ground becomes necessary. Frozen ground presentsat least two very serious obstacles to excavating STPs. First, diggingin frozen earth can be very labor intensive and time consuming. Second,frozen earth tends to remain in large clods that are resistant tosifting and screening through wire mesh. For these reasons, it isgenerally disfavored to excavate STPs in frozen ground. This reluctanceto perform STPs in freezing conditions can result in development delaysfor many months.

The project area over which STPs must be placed is often remote and/orrugged undeveloped terrain which must be traversed by foot or with theaid of off-road vehicles like four-wheelers. In Northern climates duringthe winter months, snowmobiles may be the only effective means oftransport. As a result of these often-difficult conditions, allequipment used to perform STP survey must be easily packable andtransportable by foot, four-wheeler, or snowmobile. Large and/or heavyequipment is simply impractical for performing STPs, especially duringthe winter months in Northern climates.

Moreover, State Historic Preservation Office standards, as well asguidelines established by other agencies, typically prohibit ordiscourage archaeological investigations in frozen ground, during timeswhen the ground is snow covered, or when it is snowing or rainingheavily. For this reason, the industry has avoided the development ofsolutions designed for winter field conditions.

There is therefore a need in the art to facilitate the placement of STPsin frozen ground using equipment that is easy to transport.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, a portable ground thawingsystem comprises a heat chamber having an open bottom surrounded by asidewall and a closed top. A charging inlet is disposed in the sidewall.An exhaust flue is disposed in the sidewall. A heater has a dischargenozzle configured to emit a stream of hot gas along a discharge vector.The heater is disposed proximate to the heat chamber with the dischargevector passing through the charging inlet. The flue is located generallyopposite the charging inlet.

According to a second aspect of the invention, a method is provided forexcavating a Shovel Test Pit (STP) in frozen ground. The methodcomprises the steps of: preparing a test area by clearing debris andremoving snow accumulations above a threshold limit, placing the openbottom of a heat chamber on the test area, orienting the heat chamber sothat its charging inlet is leeward and its exhaust flue is windwardrelative to the prevailing wind direction, directing a stream of hot gasfrom a heater along a discharge vector passing through the charginginlet, and circulating hot gases through a heat loft within the heatchamber above the charging inlet prior to exiting through the flue.

The system and method of this invention enable in-season soilconditions, i.e., not frozen ground, to be easily replicated for takinggeological samples and any other expedient purposes. The invention thawsearthy sediments to the point that they could be removed from the groundby standard shovel testing operation and subsequently passed through amesh during a typical screen operation. The system and method areeffective, at least in part, by controlling heated gas so as to flowconsistently across the frozen ground surface below the heat chamber. Asa result, the invention enables winter-time near-surface archaeologicaltesting to be conducted during urgent or emergency situations, such asburied utility repair, or to conduct further investigations surroundingthe inadvertent find of human remains. This invention offers a solutionto the prevailing local standards and guidelines that typicallydiscourage archaeological investigations in frozen ground.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is a perspective view of a portable ground thawing systemaccording to one embodiment of the invention;

FIG. 2 is a top view of the portable ground thawing system of FIG. 1;

FIG. 3 is a perspective view showing the heat chamber and heateraccording to an embodiment of the invention;

FIG. 4 is a simplified side elevation view, in cross-section, showingthe heat chamber and heater disposed for use over frozen ground in whichbelow the surface resides a buried artifact and a frost line;

FIG. 5 is a view as in FIG. 4 showing the section of ground below theheat chamber thawed and the baffle inverted;

FIG. 6 is a perspective view of the baffle according to one exemplaryembodiment of the invention;

FIG. 7 is a fragmentary perspective view showing the lower portion ofthe heat exchange with baffle oriented as in FIG. 4, the baffle beingmoved to a fully open position in solid and a fully closed position inphantom;

FIG. 8 is a side elevation of the heat chamber with baffle oriented asin FIG. 5, the baffle being moved to a fully open position in solid anda fully closed position in phantom; and

FIG. 9 illustrates the process of placing a shovel test pit (STP) bydigging a hole in the thawed ground, transferring soil excavated fromthe hole to a screen mesh, and sifting the excavated soil through thescreen mesh to locate artifacts.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a portable groundthawing system is generally shown in one exemplary embodiment for use inplacing shovel test pits (STPs) and such other applications as may befound expedient to excavate small portions of earth during the wintermonths in Northern climates.

The portable ground thawing system includes a heat chamber, generallyindicated at 10. The heat chamber 10 is a hollow construction having anopen bottom 12 surrounded by a sidewall 14 and a closed top 16. Thesidewall 14 can be made of steel or other suitable heat-compatiblematerial. In the illustrated examples the heat chamber 10 takes the formof a generally cylindrical volume in which case the sidewall 14 isgenerally cylindrical and the top 16 is generally circular and thebottom 12 is also generally circular. It has been discovered that acommercial grade steel drum of 30-gallon size will suffice forconstruction of the heat chamber 10. However, the heat chamber 10 cantake many different shapes and forms, including cube-like, dome-like,pyramid-like and cone-like to name a few. Naturally, other(non-cylindrical) forms of the heat chamber 10 will dictatecorresponding adaptations to the shapes of the bottom 12, top 16 andsidewall 14 features. In all contemplated variations, the open bottom 12end is posited to face the underlying ground surface.

At least one handle 18 is attached to the heat chamber 10 to facilitatehandling. It has been found expedient to attached two such handles 18adjacent the top 16, diametrically located opposite one another on thesidewall 14. The handles 18 can be economically fabricated from asection of metallic rod bent to form a D-shaped loop that is welded orotherwise affixed directly to the heat chamber 10. A thermal resistantmetal can be used, if desired, to reduce the risk of burn injury to theoperators. The loop configuration shown in the drawing is advantageousfor naturally shedding heat so as to reduce the risk of burn injury whenthe system is in operation. Of course, handles 18 of other numbers,shapes and mounted locations can be substituted for those illustrated inthe figures if desired.

A charging inlet 20 disposed in the sidewall 14. The charging inlet 20has an upper extremity 22 and a lower extremity 24. The lower extremity24 of the charging inlet 20 is axially spaced from bottom 12 by a lowerextremity distance IL. The charging inlet 20 is shown to have agenerally rectangular shape throughout the accompanying illustrations,however other shapes are certainly possible, including but not limitedto circular. Regardless of shape, the charging inlet 20 will have upper22 and lower 24 extremities. In one example, the charging inlet 20 is anopening approximately 8-inches high by 12-inches wide.

Particularly beneficial results have been achieved when the upperextremity 22 of the charging inlet 20 is axially spaced generally midwaybetween the bottom 12 and the top 16 of the heat chamber 10. Morespecifically, the upper extremity 22 is preferably located within ±10%of the midline between the bottom 12 and the top 16 of the heat chamber10. Thus, in the example of a heat chamber 10 having an overall heightof 30 inches (i.e., axial distance between top 16 and bottom 12), themidline will fall at 15 inches as measured from either end 12, 16. Thus,±10% equal 3 inches on either side of the midline. In other words, inthis example the upper extremity 22 will preferably fall between about12 inches and 18 inches as measured from the bottom 12.

In use, the heat chamber 10 is positioned so that the charging inlet 20is located on the leeward side relative to the wind direction W. Bymaintaining the upper extremity 22 of the charging inlet 20 within 10%of the midline, a substantial volume of upwardly confined space can beestablished in a heat loft 25 inside the heat chamber 10. The trappedvolume inside the heat chamber 10 above the upper extremity 22 is theheat loft 25, as indicated in FIGS. 4 and 5. In cases where the heatchamber 10 is cylindrical in shape, the heat loft 25 will, normally, belikewise cylindrical in shape as an included space. A hovering body ofhot gas is loosely contained inside the heat loft 25 region. This bodyof hot gas performs beneficial radiant and convective functions. Interms of radiant functionality, the heat loft 25 behaves like a radiantheat body directing heat energy downwardly through the open bottom 12toward the exposed ground surface. In terms of convective functionality,internal eddy currents circulate through the heat loft 25 and refreshtheir heat energy in the heat loft 25 before passing down toward theground. These heating attributes will be discussed further below inconnection with FIGS. 4 and 5. By maintaining a floating bubble of heatin this heat loft 25 region inside the heat chamber 10, rapid thawing ofthe ground can be achieved through a combination of radiant andconvective heat transfer mechanisms.

An exhaust flue 26 is disposed in the sidewall 14 to emit excess gasfrom the heat chamber 10. The flue 26 is located generally opposite thecharging inlet 20. Thus, in examples where the heat chamber 10 iscylindrical, the flue 26 can be seen as diametrically opposed to thecharging inlet 20. In use, the heat chamber 10 is positioned so that theexhaust flue 26 is located on the windward side relative to the winddirection W.

The flue 26 has a first edge 28 adjacent the bottom 12 and a second edge30 adjacent the top 16. The first edge 28 of the flue 26 is axiallyspaced from bottom 12 by a first flue distance F1, whereas the secondedge 30 is axially spaced from bottom 12 by a second flue distance F2.In practice, a first flue distance F1 of approximately 4 inches has beenfound to provide satisfactory results. The second flue distance F2 isless than or equal to the lower extremity distance IL of the charginginlet 20 on the opposite side of the heat chamber 10. That is to say,the lower extremity 24 of the charging inlet 20 may be configured so asnot to extend as low as the exhaust flue 26. As a result, cooler gaswill be more effectively forced to exit the heat chamber 10 below thelevel of the charging inlet 20.

In the illustrated examples, the flue 26 is generally rectangular, withthe first 28 and second 30 edges being parallel to one another andextending horizontally relative to the ground. In practice, a flue 26having a size of 6-inches high by 8-inches wide has been foundeffective. However, the flue 26 can take many different shapes. In somecontemplated embodiments, the flue is circular or oval. In somecontemplated embodiments, the flue is louvered.

In the illustrated examples, a baffle 32 is moveably connected to theflue 26. The baffle 32, best seen in FIGS. 6-8, may be configured withat least one directional fin 34. The directional fin 34 is outwardlyangled so as to facilitate the egress of excess gas from the heatchamber 10. Preferably, the baffle 32 is invertible in the flue 26 so asto invert the directional fin 34 to vector exiting gas upwardly (FIG. 4)or downwardly (FIG. 5). In this manner, the pattern of circulatingcurrents within the heat chamber 10 can be manipulated by the user tomaximize ground thawing performance.

Furthermore, a moveable interface 36 can be incorporated to support thebaffle 32 for movement relative to the flue 26. The moveable interface36 is shown in one exemplary form in FIG. 6 as a curved slot-likeformation in a curved L-shaped flange 38 on the baffle 32. The curvatureof the slot and of the L-shaped flange 38 match the curvature of thesidewall 14 so that an even fit is maintained therebetween. As perhapsbest understood from FIGS. 7 and 8, the L-shaped flange 38 is adapted tohook over either the second edge 30 (FIG. 7) or the first edge 30 (FIG.8). The slot-like moveable interface 36 is threaded onto the sidewall14. A gentle torque is created by the outward handing directional fin34, thus causing the edges of the slot-like moveable interface 36 togrip on the sidewall 14 holding the baffle 32 in position. In use, anoperator can slide the baffle back-and forth horizontally to adjust theexit area of the flue 26, thereby controlling the build-up of heatinside the heat chamber 10. In FIGS. 6 and 7, the flue is shown slid tofull-open positions in solid, and to full closed positions in phantom.

Those of skill in the art will readily appreciate alternative designs bywhich to achieve a moveable interface 36. In one contemplatedembodiment, relative sliding movement between baffle 32 and flue 26 isachieved by seating a suitably configured baffle in external tracksaffixed to the sidewall 14 above and below the flue 26. In this example,the tracks are open at each end enabling the baffle 32 to be removed,inverted, then re-installed in the tracks. In another contemplatedembodiment, the baffle 32 is rotatably attached relative to the flue 26with features enabling both redirection of exhaust (via directional fin34) and alteration of the flue 26 exhaust area. In still othercontemplated embodiments, the baffle 32 can be mechanized to effectdirectionality and restrictions much like the vent controls found inpassenger cars and other HVAC applications. Indeed, many alternativedesigns are possible and within the scope of the person having ordinaryskill in this art.

The ground thawing system further includes a portable heater, generallyindicated at 40 in FIGS. 1-5. The heater 40 can be any suitable type,but in the illustrated examples comprises the well-known and ubiquitousvariety of portable forced-air or convection space heaters, often usingkerosene or propane as fuel but also requiring electricity. In practice,a heater 40 rated at approximately 155,000-BTU has been found to providesatisfactory results. Such heaters are often found at constructionsites. Heaters 40 of this type are variously referred to as “torpedo” or“salamander” furnaces. The heater 40 has a discharge nozzle 42configured to emit a stream of hot gas along a discharge vector V. Theheater 40 is disposed proximate to the heat chamber 10 with thedischarge vector V passing through the charging inlet 20 as shown in theseveral figures.

A mounting base supports the heater 40 at an incline so that thedischarge vector V passes through the charging inlet 20 in a downwardtrajectory. The mounting base can be any of several forms, includingbi-pod and tripod arrangements, as well as mechanically adjustable tilttables. In the illustrated examples, however, the mounting base isdepicted in the basic but effective form of a generally flat sub-base 44combined with a plurality of shims 46. The shims 46 serve as easilyadjustable props when disposed between the sub-base 44 and the heater 40to achieve the desired downward trajectory of the discharge vector V.Simplicity is favored in view of the need to transport the components ofthe system over harsh terrain during cold weather as well as avoidingunnecessary mechanical function that would be subject to freezing andinoperability.

To supply electrical power to the heater 40, an electricity generator 48is provided with appropriate electrical extension cord. A fuel source 50is also provided for supplying suitable combustible fuel to the heater40. In FIGS. 1 and 2, the fuel source 50 is depicted as a propane tankwhich will be suitable for heaters 40 configured to burn propane. Inother contemplated embodiments, the fuel source 50 could be a keroseneor fuel oil tank which would be suitable for heaters 40 configured toburn fuel oil. Naturally, accommodations can be made for the type offuel required by the heater 40.

The method of using the system to thaw frozen ground will now bedescribed. In particular, a novel cold weather method is provided forreplicating in-season soil conditions, i.e., not frozen ground, suchthat sediments are thawed to the point they can be removed from theground by standard shovel testing operation (no chipping or hacking) andpass through mesh of specified size during typical screen operation. Inone example, the mesh size is approximately 0.635-centimeter(0.25-inch).

A designated test area 52 (FIG. 1) larger than the footprint of the heatchamber 10 is first cleared of loose debris until the ground or groundcover is exposed as best possible. Uneven ground surface may prevent theheat chamber 10 from lying flush on the ground. Ground cover includestree leaves, evergreen, moss, dune grass, lawn grass, etc. Prevailingwind direction W is determined. The heat chamber 10 is placed in thecenter of the prepared test area 52 with its open bottom 12 facing theground. The heat chamber 10 is rotated, as needed, so that its flue 26is pointing windward and its charging inlet 20 is leeward relative tothe wind direction W.

In some cases, it may be desirable to leave a threshold limit of snow onthe ground. In practice, a threshold limit of 4-6 inches has been foundsatisfactory. Leaving a thin layer of snow on the test site 52 may helpreduce the risk of biomass ignition and the melt-water expedites thethawing process. Also, the heat chamber 10 will eventually sink towardthe ground, helping to seal any gaps created by an uneven groundsurface. In operation, additional snow can be shoveled around the bottom12 of the heat chamber 10, if desired, to maintain a seal due to unevenground features and produce additional melt-water.

A suitably rated heater 40 is placed on mounting base supports 44, 46 soas to direct hot gas into the charging inlet 20 along a downwarddischarge vector V. The nozzle of the heater 40 is preferably positionedabout 2 to 3 inches from the charging inlet 20. Operative connectionsare made between the heater 40 and its sources 48, 50 of electricity andfuel.

To commence the thawing operation, the heater 40 is ignited so as toforce a jet stream of hot gas through the charging inlet 20 at adownward angle V that is also pointing in the upwind direction. Byreference to FIGS. 4 and 5, it will be understood that by locating theflue 26 close to the ground and directly opposite the charging inlet 20,hot gas is drawn across the ground surface and exits through the flue26. Also, a swirling gas flow is generated within the heat chamber 10that swirls into the heat loft 25 in a looping pattern that naturallyescapes through the flue 26. The heat chamber 10 is thus intentionallydesigned to prevent the escape of gas from the heat chamber through thecharging inlet 20. It would be undesirable for the hot gas to escapethrough the charging inlet 20 due to the likelihood of blow-back on theheater 40. Built-in safety switches are common in commercial gradeheaters 40. In the event of blow-back, the heater 40 would automaticallyshut down thus halting the thawing operation.

Considering the desire to avoid blow-back, one might incorrectly assumethat the heat chamber 10 should be rotated on the test area 52 so thatits charging inlet 20 is pointing windward and its flue 26 is leewardrelative to the wind direction W—i.e., opposite to that described inthis present method. Logic would seem to indicate (incorrectly as itturns out) that if the charging inlet 20 is pointed windward, that windpressure would assist in preventing blow-back and even help inevacuating exhaust gasses through the flue 26. However, the presentinvention defies natural logic by orienting the inlet 20 and flue 26features as previously specified. The novel arrangement of elevatedcharging inlet 20 relative to flue 26 combined with a downwardlydirected discharge vector V produces a powerful and effective naturalswirling flow of gasses within the heat chamber 10. The induced currentsare sufficiently powerful to overcome the pressure of the wind W, suchthat the wind pressure can be exploited to supplement the effects of thebaffle 32. That is to say, the wind W provides (to the degree available)additional back-pressure against the escaping gases, thus enabling theoperator more control over temperature stabilization inside the heatchamber 10. Additionally, wind W blowing into the rear of the heater 40can produce negative operating effects.

As previously mentioned, a relatively large heat loft 25 establishedinside the heat chamber 10 above the charging inlet 20 performsbeneficial radiant and convective functions. As a radiant heat body, theheat loft 25 continuously projects heat energy through the open bottom12 onto the exposed ground surface. Convectively, internal currentscirculating through the heat loft 25 recharge with high heat energybefore circulating across the ground surface. Thus, the intentionallyinduced swirling gas flow as indicated in FIGS. 4 and 5 within the heatchamber 10 produces a constant sweep of hot gas across the ground beforeescaping through the flue 26.

By manipulating the baffle 32 via the moveable interface 36, theinternal currents can be adjusted and altered in relation to ambientconditions to maintain the desired internal temperatures inside the heatchamber 10. If the wind W is blowing more or less strongly, or more orless consistently, the operator may wish to orient the baffle 32 toeither of the inverted positions represented in FIGS. 4 and 5. Likewise,the temperature inside the heat chamber 10 can be regulated by adjustingthe area of the flue 26. That is, by sliding the baffle 32back-and-forth, more or less restriction to exhaust can be controlled.In mild ambient conditions it may be necessary to maximize the flue 26opening, whereas in extreme low ambient temperatures it may be desirableto minimize the flue 26 opening. Experimentation will indicate thebetter baffle 32 orientation and position relative to the flue 26.

It has been found that in at least some sub-freezing climates, an STPcan be completed using the method described above in approximately onehour on average replicating field-season ground conditions where groundcover was present (excluding lawn grass). In cases where lawn grasscover was present, or no ground cover was present, STPs could becompleted on average in approximately three hours replicating normalfield conditions. It is suspected that rather than the ground coveritself causing significant differences in time, the variance may insteadbe attributable to the amount of moisture present below a grassy groundsurface trapped within finer, less-well-drained sediments.

Once field-season ground conditions have been replicated, the heater 40is switched off and removed from the test area 52. The heat chamber 10is also removed from the test area 52 with the aid of the handles 18 toavoid burn-related injury. In the thawed earth, an STP can be excavated.In some cases, a suitable STP may be hand-dug with shovel 54, asdepicted in FIG. 9, to a depth of about 50 cm (20 in) and having atypical diameter of about 35-40 cm (14-16 in). The actual depth to beexcavated can vary from one test area 52 to the next. In general, theobjective is to stop digging upon encountering either sterile subsoil orbedrock or impermeable gravel/rock concentrations.

Soil from the STP is passed through suitably sized mesh 56 to identifyartifacts 58. Information about the soils observed in each STP istypically recorded in a field logbook to assist with interpretation ofhow the site deposits formed over time and to help evaluate whether soildisturbances have occurred. Upon completion of the STP, the excavatedsoil is returned to the hole and tamped down in an effort to return thetest area 52 to its initial condition.

The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and fallwithin the scope of the invention.

What is claimed is:
 1. A portable ground thawing system comprising: aheat chamber having an open bottom surrounded by a sidewall and a closedtop, a charging inlet disposed in said sidewall, an exhaust fluedisposed in said sidewall, a heater having a discharge nozzle configuredto emit a stream of hot gas along a discharge vector, said heaterdisposed proximate to said heat chamber with said discharge vectorpassing through said charging inlet, and said flue being locatedgenerally opposite said charging inlet.
 2. The system of claim 1 whereinsaid heat chamber is a generally cylindrical volume as defined by agenerally cylindrical said sidewall and a generally circular said topand a generally circular said bottom, said flue being diametricallyopposed to said charging inlet.
 3. The system of claim 1 wherein saidcharging inlet has an upper extremity and a lower extremity, said lowerextremity being axially spaced from bottom by a lower extremity distance(IL), said flue having a first edge adjacent said bottom and a secondedge adjacent said top, said second edge being axially spaced frombottom by a second flue distance (F2), said second flue distance (F2)being less than or equal to said lower extremity distance (IL).
 4. Thesystem of claim 1 wherein said charging inlet has an upper extremity anda lower extremity, said upper extremity being axially spaced within 10%of a midline between said bottom and said top of said heat chamber. 5.The system of claim 1 further including a baffle moveably connected tosaid flue.
 6. The system of claim 5 further including a moveableinterface supporting said baffle for sliding movement relative to saidflue.
 7. The system of claim 5 wherein said baffle has at least onedirectional fin.
 8. The system of claim 7 wherein said baffle isinvertible in said flue so as to turn said directional fin upside downin use.
 9. The system of claim 1 further including a mounting basesupporting said heater at an incline so that said discharge vectorpasses through said charging inlet in a downward trajectory.
 10. Thesystem of claim 1 wherein said heat chamber is a generally cylindricalvolume as defined by a generally cylindrical said sidewall and agenerally circular said top and a generally circular said bottom, saidflue being diametrically opposed to said charging inlet, furtherincluding a pair of handle loops attached to heat chamber, said handleloops being diametrically arranged from one another on said sidewall.11. The system of claim 1 wherein said heat chamber is a generallycylindrical volume as defined by a generally cylindrical said sidewalland a generally circular said top and a generally circular said bottom,said flue being diametrically opposed to said charging inlet, and atleast one of said charging inlet and said flue being generallyrectangular.
 12. The system of claim 11 wherein said flue having firstedge adjacent said bottom and a second edge adjacent said top, saidfirst edge of said flue being axially spaced from bottom by a first fluedistance (F1), further including a baffle moveably connected to saidflue, said baffle has at least one directional fin, said baffle beinginvertible in said flue so as to turn said directional fin upside downin use, and a moveable interface supporting said baffle for slidingmovement relative to said flue.
 13. The system of claim 1 furtherincluding an electricity generator for supplying electrical power tosaid heater.
 14. The system of claim 1 further including a fuel sourcefor supply combustible fuel to said heater, said fuel source comprisinga propane tank.
 15. A portable ground thawing system comprising: a heatchamber having an open bottom surrounded by a sidewall and a closed top,said heat chamber being a generally cylindrical volume as defined by agenerally cylindrical said sidewall and a generally circular said topand a generally circular said bottom, a pair of handles attached to heatchamber, each said handle comprising a loop extending from said sidewalladjacent said top, said handles being diametrically arranged from oneanother on said cylindrical sidewall, a charging inlet disposed in saidsidewall, said charging inlet having an upper extremity and a lowerextremity, said lower extremity being axially spaced from bottom by anlower extremity distance (IL), said upper extremity being axially spacedgenerally midway between said bottom and said top of said heat chamber,said charging inlet being generally rectangular, an exhaust fluedisposed in said sidewall, said flue being diametrically opposed to saidcharging inlet, said flue having first edge adjacent said bottom and asecond edge adjacent said top, said first edge of said flue beingaxially spaced from bottom by an first flue distance (F1), said secondedge of said flue being axially spaced from bottom by a second fluedistance (F2), said second flue distance (F2) being less than or equalto said lower extremity distance (IL), said flue being generallyrectangular, a baffle moveably connected to said flue, said bafflehaving at least one directional fin, said baffle being invertible insaid flue, a moveable interface supporting said baffle for slidingmovement relative to said flue, a heater having a discharge nozzleconfigured to emit a stream of hot gas along a discharge vector, saidheater disposed proximate to said heat chamber with said dischargevector passing through said charging inlet, a mounting base supportingsaid heater at an incline so that said discharge vector passes throughsaid charging inlet in a downward trajectory, said mounting baseincluding a generally flat sub-base, said mounting base including aplurality of shims disposed between said sub-base and said heater, aelectricity generator for supplying electrical power to said heater, anda fuel source for supply combustible fuel to said heater.
 16. A methodfor placing a Shovel Test Pit (STP) in frozen ground comprising thesteps of: preparing a test area by clearing debris and removing snowaccumulations above a threshold limit, positioning a heat chamber havingan open bottom on the test area, orienting the heat chamber so that acharging inlet thereof is leeward and an exhaust flue thereof iswindward relative to the prevailing wind direction, directing a streamof hot gas from a heater along a discharge vector passing through thecharging inlet, and circulating hot gases through a heat loft within theheat chamber above the charging inlet prior to exiting through the flue.17. The method of claim 16 further including the step of pointing thedischarge vector in a downward trajectory as it passes through thecharging inlet.
 18. The method of claim 16 further including the step ofinverting a baffle in the flue to manipulate the flow of exhaust gasesthrough the flue.
 19. The method of claim 16 further including the stepof moving a baffle relative to flue to constrict the exit flow rate ofexhaust gases through the flue.
 20. The method of claim 16 furtherincluding the steps of: removing the heat chamber from the test areawhen the underlying ground is thawed, digging a hole in the thawedground, transferring soil excavated from the hole to a screen mesh,sifting the excavated soil through the screen mesh, removing anyartifacts captured by the screen mesh, and returning the sifted soil tothe hole.